FTIR spectroscopic and quantum-chemical studies on some tribromoindenes and their isomers

Combined experimental and computational studies on molecular structure of newly synthesised transtirans 1,2,3-tribromo-1,2,3-trihydro-¹H-benz[f]indene (TTTBI) were reported. Also, only computational studies were done for cis-trans-1,2,3-tribromo-1,2,3-trihydro-¹H-benz[f]indene (CTTBI) and cis-cis-1,2,3-tribromo-1,2,3-trihydro-¹H-benz[f]indene (CCTBI) in order to understand the vibrational spectra and molecular parameters of them. The geometry optimization and vibrational wave numbers of the title molecules were carried out with the Gaussian98 program package by using Hartree-Fock (HF) and Density Functional Theory (DFT) with B3LYP functional and 6–31G (d) basis set. All calculations were done for the title compounds in their ground states. Especially for CTTBI and CCTBI, which could not be synthesized yet, these kind of pre-calculations take an important role for their synthesis process. Also crystal structural parameters of TTTBI by single-crystal X-ray diffraction method was used as input for computational study of it. Observed and calculated vibrational wave numbers were compared. Because the use of benz[f]indene as a cyclopentadienyl ligand attracted much attention because an annulated benzo ring might increase both the stereocontrol and productivity of catalytic system, TTTBI and other computationally studied and modeled two molecules may play an important role of other types of compounds as a starting structures.     

FTIR spectroscopic studies of the matrix photoionization and photolysis products of methylene halides

Matrix photoionization of methylene bromide produced absorptions at 1019, 897, and 788 cm^?1 identified previously as CBr₂⁺, CHBr₂⁺, and CHBr₂. High-resolution FTIR spectra revealed overlapping 1/2/1 triplets for natural bromine isotopes with individual linewidths near 0.2 cm^?1. New absorptions at 3121, 2897, and 1345 cm^?1 are assigned to the (CH₂Br⁺)Br cation complex which yields CHBr₂⁺ on photolysis. A substantially increased yield of the CHCl₂⁺ species made possible observation of the CH stretching mode at 3033 cm^?1 and the symmetric CCl₂ stretching mode at 845 cm^?1 along with the previously observed stronger 1291- and 1044-cm^?1 fundamentals. The high resolution and enhanced signal-to-noise capability of the FTIR are clearly demonstrated in this investigation.     

Mid-infrared spectroscopic studies and lasing in GaAs–AlGaAs quantum cascade devices

Complementary intersubband and interband optical measurements have been employed in order to study GaAs–AlGaAs quantum cascade light-emitting diode and laser structures. Using these techniques, we have measured the redistribution of electrons throughout the bridging regions and upper states in the active regions of the diode device with increasing bias. The high quality of the sample gives very narrow line widths in the optical spectra, permitting the resolution of transitions involving closely spaced energy levels. This has allowed the direct observation of level alignment at the onset of current flow through the device. In addition, stimulated emission at λ=9.7 μm has been observed from a GaAs–AlGaAs laser structure under pulsed operation. A threshold current density of 6.5 kA/cm² and peak power 300 mW are measured at 10 K and lasing operation is observed up to 200 K.     

蚕豆病害叶的FTIR研究

用傅里叶变换红外光谱技术结合统计分析对蚕豆锈病、茎基腐病、轮纹病、黄化卷叶病和正常叶片进行鉴别研究。结果显示病害叶片和正常叶片的红外图谱相似,仅有几个吸收强度比存在差异;对光谱进行二阶导数分析发现,病害叶片和正常叶片的二阶导数光谱在1 200～700cm-1范围差异明显,对该区域内的光谱数据进行相关分析、主成分分析和聚类分析,结果显示,正常叶片之间、同种病害样品之间相关系数都在0.928以上,而病害叶片和正常叶片以及不同病害样品之间的相关系数降低;45个样品聚类分析和主成分分析正确率分别为73.3%和82.2%。傅里叶变换红外光谱技术具有快速、无损、准确等优点,有望为蚕豆病虫害诊断提供新的方法与途径。     

赤铁矿和三羟铝石吸附Cu~(2+)的红外光谱研究

应用红外光谱法,研究了不同pH值和Cu2+浓度条件下,合成赤铁矿和三羟铝石吸附Cu2+后表面羟基结构及其特征吸收峰的变化。结果表明:(1)随Cu2+浓度增加,赤铁矿表面H—O—H和OH的变形振动参与了吸附反应,Cu2+强烈地缔结在Fe—O上,形成了Fe—O—(Cu)结构。(2)酸性条件下,H+破坏了赤铁矿表面的O—H结构,NO3-促使弱峰1 131 cm-1的产生。随pH值增大,赤铁矿表面OH-逐渐由伸缩振动转变为变形振动,Fe—OH和Fe3+—O2-结构不断发生改变。(3)三羟铝石对Cu2+的吸附发生在高波位,随Cu2+浓度增大,其表面游离羟基的O—H弯曲振动、水分子的OH-伸缩振动和H—O—H弯曲振动均参与了吸附反应,Al—O基中的Al3+渐被Cu2+取代从而加强了较低波位的振动强度。(4)随pH值增加,三羟铝石Al—OH的弯曲振动和Al—O的伸缩振动逐渐发生着改变,表明吸附Cu2+后,在其表面形成了AlOCu+与AlOCuOH结构。     

Joint Raman spectroscopic and quantum chemical analysis of the vibrational features of Cs2RuO4

The Raman spectroscopic characterization of the orthorhombic phase of Cs₂RuO₄ was carried out by means of group theory and quantum chemical analysis. Multiple models based on ruthenate (VI+) tetrahedra were tested, and characterization of all the active Raman modes was achieved. A comparison of Raman spectra of Cs₂RuO₄, Cs₂MoO₄, and Cs₂WO₄ was also performed. Raman laser heating induced a phase transition from an ordered to a disordered structure. The temperature‐phase transition was calculated from the anti‐Stokes/Stokes ratio and compared with the ones measured at macroscopic scale. The phase transition is connected with tilting and/or rotations of RuO₄ tetrahedra, which lead to a disorder at the RuO₄ sites. © 2015 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd.     

FTIR spectroscopic characterization of the adsorption and desorption of ammonia on MgO surfaces

In the present paper an attempt is made to disentangle the complex IR spectra obtained in the course of the adsorption of NH₃ on high surface area MgO. For this purpose two simplifications were introduced in comparison to previous studies: (a) Only uniformly hydroxylated MgO surfaces (degassing temperature: 200 °C) and completely dehydroxylated MgO surfaces (degassing temperature: 1000 °C) were used as adsorbent, (b) The equilibrium pressure of the adsorbate NH₃ was generally maintained below 200 Pa in all adsorption and desorption experiments. Under these conditions the position and the pressure dependence of the resulting bands may consistently be interpreted in terms of characteristic surface species. Only the completely dehydroxylated MgO surface gives rise to a heterolytic dissociation into neighbouring NH₂ and OH groups. In addition, NH₃ is physically adsorbed on less reactive sites via diverse types of hydrogen bonds. Less well defined hydroxylation states give rise to considerably more complicated spectra. In a first approximation they may be constructed by linearly combining two spectral patterns, one related to a uniformly hydroxylated and the other to a dehydroxylated surface. NH₃ pressures around and beyond 1 kPa give rise to significant changes of band positions and band shapes compared to those observed below 200 Pa. The interpretation of these effects which have previously been ignored must necessarily rely on more complicated models.     

Vibrational studies of polar aprotic molecule in aromatic chemical and isotropic solvents: experimental and quantum chemical investigations

Raman spectroscopic technique has been used to study the intermolecular interactions and dynamics of SO, C―H and CSC stretching modes of dimethyl sulfoxide (DMSO) in binary mixtures using methyl benzene (MBN) and deuterated methyl benzene (MBNd) aromatic solvents. The Raman band of SO stretching mode has been deconvoluted into four distinct bands for neat DMSO as well as in binary mixtures. Deconvoluted bands in neat DMSO were assigned as monomer, cyclic out‐of‐phase, cyclic in‐phase and chain dimers having peak wavenumbers 1069.10, 1056.60, 1041.50 and 1027.30 cm⁻¹ respectively. Peak wavenumber of SO stretching mode shows red shift, while peak wavenumbers of C―H and CSC stretching modes show blue shift with the increase in solvent concentration. The vibrational relaxation phenomena for all the stretching modes have been studied as a function of solvent concentration. Quantum‐chemical calculations have been carried out to gain more insight into the self‐association of DMSO and in interacting environment with the solvents using ab initio and density functional theory method. The ab initio basis set is HF/6‐31 + G (d, p) for the interacting system. The hydrogen bond complexes of DMSO with MBN and MBNd using IEF‐PCM model have been calculated using B3LYP functional and 6‐31 + G(d,p) basis sets. Theoretical calculations have been compared with the experimental findings and we obtained good coherence of the results. Copyright © 2015 John Wiley & Sons, Ltd.     

化学反应中的量子干涉

波长为157nm的 O2 在受激准分子激光器作用下可离解为 O3P 和 O1D .为了在理论上研究化学反应 的量子干涉效应,利用一阶含时波恩近似及各向异性相互作用势建立了量子干涉效应模型,讨论了完全干涉和完全非干涉两种情况。     

Conformational analysis and vibrational spectroscopic studies on dapsone

In this study, the theoretical conformation analysis of free dapsone has been performed by single point energy calculations at both semi-empirical PM3 and DFT/B3LYP-3-21G theory levels and three stable conformers were determined. Both the IR and Raman spectra of the molecule in solid phase have been recorded. The IR intensities and harmonic vibrational wavenumbers of each conformer were calculated by DFT method at B3LYP/6-31++G(d,p) theory level. For the fundamental characterization, the total energy distribution (TED) calculations of the vibrational modes were done using parallel quantum mechanic solution program (SQM) and the fundamental modes were assigned. The theoretical results are in agreement with the experimental ones.     

Assembly of quantum dots on peptide nanostructures and their spectroscopic properties

We present a chemical process for the decoration of self-assembled two-dimensional peptide fibrils with two different sizes of CdSe@ZnS core–shell quantum dots (Qdots) capped with trioctylphosphine oxide molecules. The attachment of the semiconducting nanoparticles to the fibrils is directed via disulfide bond between the quantum dot and cysteine aminoacids that are deliberately impeded in the peptide structures. A significant red shift in the emission spectra of the quantum dots is observed and attributed to the synergistic interaction between adjacent nanoparticles arranged on peptide film templates extending over hundreds of nanometers.     

FTIR spectroscopic study for improving material preparation of high Tc superconductors

FTIR spectroscopic studies have been carried out to understand high Tc superconductor YBa₂Cu₃O_7−δ during growth process. Characteristic IR absorption bands of the material are compared with those of the constitutent compounds to determine the presence of unused components and the completion of solid state reactions. IR spectroscopy has been found to be very convenient in such investigations.     

Structural studies on banana oil,isoamyl acetate,by means of microwave spectroscopy and quantum chemical calculations

The rotational spectrum of isoamyl acetate, H₃C–COO–(CH₂)₂–CH(CH₃)₂, has been recorded and assigned using a molecular beam Fourier transform microwave (MB-FTMW) spectrometer in the frequency range of 3–26.5?GHz. One conformer has been observed. By comparing the spectroscopic data with the quantum chemical data, it was found that the conformer observed does not have C_s symmetry. The rotational and centrifugal distortion constants were determined. The barrier to internal rotation of the acetate methyl group was found to be 93.98?cm^?1. Due to the high number of the conformers, a systematic nomenclature will be presented.     

Experimental and quantum chemical calculational studies on 2-[(4-propylphenylimino)methyl]-4-nitrophenol

The Schiff base compound 2-[(4-propylphenylimino)methyl]-4-nitrophenol has been synthesized and characterized by IR, UV–Vis, and X-ray single-crystal determination. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree–Fock (HF) and density functional theory (DFT) with the 6-31G(d) basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behaviour of the title compound in solvent media was examined using the B3LYP method with the 6-31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provides a more stable structure than Onsager's method. Using the TD-DFT method, electronic absorption spectra of the title compound have been predicted and good agreement with the TD-DFT method and the experimental determination was found. The predicted nonlinear optical properties of the title compound are much greater than those of urea. In addition, DFT calculations of the molecular electrostatic potential and NBO analysis of the title compound were carried out at the B3LYP/6-31G(d) level of theory.     

FTIR free-jet set-up for the high resolution spectroscopic investigation of condensable species

An existing experimental set-up combining Fourier transform infrared (FTIR) spectroscopy and free-jet cooling has been modified significantly to allow high resolution studies of the spectrum of monomer species which are liquid under standard conditions. Evaporation of the liquid samples is controlled by a condenser apparatus which is described. A supersonic planar expansion issuing from a narrow aperture is preferred for its very high cooling rate. Such an expansion, probed with a pitot tube, has a zone of limited temperature gradient close to the nozzle exit. The continuum isentropic model appears well suited to describing the thermodynamic properties of the flow up to a high number of nozzle diameters downstream. High resolution spectra of benzene and methanol have been recorded in the 3 μm wavelength range, and their analysis demonstrates a well defined rotational temperature in the 20–25 K range.     

Vibrational spectra and scaled quantum chemical studies of the structure of Martius yellow sodium salt monohydrate

The FT‐IR and Raman spectra of Martius Yellow sodium salt Monohydrate (MYM) [2, 4‐dinitro‐1‐naphthol sodium salt] in solid‐phase have been measured. The geometry, intramolecular hydrogen bonding and harmonic vibrational wavenumbers of MYM have been investigated with the help of B3LYP density functional theory (DFT) methods. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The existence of intramolecular C H···O improper, blue‐shifted hydrogen bonding was investigated by means of the NBO analysis. The infrared and Raman spectra were predicted theoretically from the calculated intensities. The observed and the calculated spectra were found to be in good agreement. Copyright © 2009 John Wiley & Sons, Ltd.     

FTIR and spectroscopic ellipsometry investigations of the electron beam evaporated silicon oxynitride thin films

FTIR and variable angle spectroscopic ellipsometer in conjunction with computer simulation were employed to investigate the electron beam evaporated SiO_xN_y thin films. FTIR showed a large absorption band located between 600 and 1250 cm⁻¹, which indicates that Si-O and Si-N bands are overlap in SiO_xN_y films. A three layers model was used to fit the calculated data to the experimental ellipsometric spectra. The main layer was described by Cauchy model while the interface layer and the surface layer were described using Tauc-Lorenz oscillator and Bruggeman effective medium approximation, respectively. The thickness, the refractive index and the extinction coefficient were accurately determined. The refractive index at 630 nm was found to increase from 1.74 to 1.85 with increasing the film thickness from 191.6 to 502.2 nm. The absorption coefficient was calculated from the obtained extinction coefficient values and it has been used to calculate the Tauc and Urbach energies.